This invention relates to a picking control apparatus for looms in which even when the flying characteristic of filling yarns is varied in a jet room, stable picking operation can be continued.
In a jet room, particularly in an air jet room, picking sometime becomes unstable due to a change in flying characteristic of filling yarns used for weaving. This unstable phenomenon is considered to result mainly from the fact that yarn properties such as coarseness of yarns, sizes of fuzz and the like vary in a longitudinal direction whereby air resistance of yarns changes.
In view of the foregoing, various procedures have been proposed in order to continue a stable picking operation even when the flying characteristic of filling yarns is varied. According to the most representative procedure, a loom mechanical angle, (hereinafter referred to as a weft arrival angle) in which a filling yarn having a predetermined length arrives at the opposite side of picking of woven cloth is monitored. A variation in flying characteristic of filling yarns is grasped by the change of the arrival angle, and a loom mechanical angle (hereinafter referred to as a start angle) at which picking operation starts accordingly as well as injection pressures of a main nozzle and a sub-nozzle for picking are controlled.
The aforementioned control is accomplished in a manner such that, for example, when a delay of the arrival angle is detected because the flying characteristic of filling yarns lowers, the start angle is quickened and injection pressure is increased in order to correct such a delay. On the other hand, with respect to the lead of the arrival angle, both the start angle and injection pressure are controlled reversely of the former to thereby maintain a constant arrival angle, which obtains a better result than the case where only one of the start angle and the injection pressure is controlled. That is, in the case where only the start angle is corrected, time balance with weft shedding becomes broken, and as a result, defective picking such as so-called warp engagement, blow-off of filling yarns and the like is liable to occur. On the other hand, in the case where only the injection pressure is corrected, there was a problem in that it cannot precisely follow the variation of the flying characteristic of filling yarns due to the slow response thereof.
However, even when both the start angle and the injection pressure are controlled, problems remain as follows. That is, since correction information based on the advance or delay of the arrival angle is merely transmitted simply parallel to control systems for controlling the start angle and the injection pressure, and therefore, it is difficult to continue stable picking operation in a real machine for the reason mentioned below.
Generally, the responsiveness of the picking member to the change of the start angle is high but the time responsiveness to the change of the injection pressure is limited. Accordingly, when the advance or delay arrival angle occurs, information of which is applied in parallel to both the control systems, the correction of the start angle, which is excellent in responsiveness, is first effected, and the correction of the injection pressure is then effected. Therefore, if the arrival angle is returned to its normal state by the correction of the start angle, the later correction of the injection pressure need not be conducted. In other words, the correction of the injection pressure is effected only in the case where even if the start angle is corrected to a correction limit determined in terms of the warp shedding, the advance or delay of the arrival angle still remains. Yet, even if the advance or delay of the arrival angle is overcome by the correction of the injection pressure, the start/angle is not pulled back from the correction limit.
For the reason described above, there was an inconvenience in that the later operation of the loom is carried out in the state where the start angle is at a correction limit, making it extremely difficult to realize continuation of a stable picking operation.